The biggest issue wasn’t the 10 years requirement but rather that when you somehow couldn’t fulfill it (moving or such), the time would reset and might be wasted.
https://www.buzer.de/gesetz/5521/al25428-0.htm
Shortly after, in July 2011, the requirement for Wehrdienst was dropped altogether. Can't access older versions but there has been a history of reductions in lengths for the "normal" Wehrpflicht, so it probably followed suit: https://de.wikipedia.org/wiki/Wehrpflicht_in_Deutschland#Bun...
THW was seen as the really easy way out of the draft (if you could get a spot), because emergencies were rare and weekend exercises were "easy". Informally THW stood for "Trinken, Helfen, Weitertrinken", "Drinking, Helping, Continued Drinking".
I believe that the other commenters said that you could "commit" to being a volunteer for 10 years and thus could avoid mandatory military service. This is the part that was not clear.
When I remember right, 3-4 out of my class avoided subscription like that (many on other ways).
There was military service, which was the shortest.
The there was civil service which was longer.
Then there was disaster relive service which was even longer. But you only had to train every other weekend or so and help at disasters and not do it full time in one swing.